I can see you used a lot of little bricks: use the largest bricks you can
Your cannon barrels are disconnected from the base: use something flat to connect them
The emitters for the propulsion is a poor choice unless it's fairy dust
Very boxy, the bottom and rear top could use some sloping
You have good length slope. You have bad width sloping
The outer engines shouldn't just be chillin ' out half off the ship, that doesn't make sense structurally
The front is a very sudden stop. Lengthen it a little.
This one is a personal pet peeve, but by most standards it's good:
It's not a good scale. If a person is a 1x1x.6 space, your ship is 6 people wide and about 12 long
That's like a fighter jet.
But like I said that ones a personal peeve, overall it's nice